Water resistant composition and heat-sensitive recording sheet containing the same

Abstract

This invention relates to a water resistant composition which comprises (A) polyvinyl alcohol, (B) a chitosan of which aqueous 1% solution has a viscosity not greater than 70 centipoise at 20 DEG C. and (C) an aldehyde compound, as well as a heat-sensitive recording sheet which comprises said composition. The composition has excellent water resistant properties and the heat-sensitive recording sheet has improved color forming properties and excellent resistance to water and solvents.

What is claimed is: 
     
       1. A heat-sensitive recording sheet comprising a support having provided thereon with a heat-sensitive color forming layer, wherein (A) polyvinyl alcohol, (B) a chitosan of which aqueous 1% solution has a viscosity not greater than 70 centipoise at 20° C. and (C) an aldehyde compound are incorporated into, or applied onto, said heat-sensitive color forming layer. 
     
     
       2. A heat-sensitive recording sheet as claimed in claim 1, wherein said aqueous 1% solution of said chitosan (B) has a viscosity of from 1 to 30 centipoise at 20° C. 
     
     
       3. A heat-sensitive recording sheet as claimed in claim 2, wherein said aqueous 1% solution of said chitosan (B) has a viscosity of from 1 to 10 centipoise at 20° C. 
     
     
       4. A heat-sensitive recording sheet as claimed in claim 1, wherein said aldehyde compound (C) is a water soluble aldehyde compound. 
     
     
       5. A heat-sensitive recording sheet as claimed in claim 4, wherein said aldehyde compound (C) is one or more compounds selected from the group consisting of water soluble monoaldehydes, polyaldehydes, condensation products of amines and formalin, methylolamides, urea formalin resins and melamine formalin resins. 
     
     
       6. A heat-sensitive recording sheet as claimed in claim 5, wherein said aldehyde compound (C) is glyoxal or hexamethylenetetramine. 
     
     
       7. A heat-sensitive recording sheet as claimed in claim 1, wherein the ratio by weight of said polyvinyl alcohol (A) to said chitosan (B); [(A)/(B)] is from 99/1 to 50/50 and the ratio by weight of said polyvinyl alcohol (A) and said chitosan (B) to said aldehyde compound (C); {[(A)+(B)]/(C)} is from 100/1 to 100/20. 
     
     
       8. A heat-sensitive recording sheet as claimed in claim 1, wherein said polyvinyl alcohol (A) is a modified polyvinyl alcohol having silyl group in the molecule. 
     
     
       9. A heat-sensitive recording sheet as claimed in claim 8, wherein said modified polyvinyl alcohol (A) having silyl group in the molecule is a hydrolyzed product of a copolymer of a vinyl ester and an olefinically unsaturated monomer having silyl group in the molecule. 
     
     
       10. A heat-sensitive recording sheet as claimed in claim 8, wherein said modified polyvinyl alcohol (A) contains from 0.01 to 10% by mole of silyl group-containing monomer units. 
     
     
       11. A heat-sensitive recording sheet as claimed in claim 8, wherein said modified polyvinyl alcohol (A) contains from 0.1 to 5% by mole of silyl group-containing monomer units. 
     
     
       12. A water resistant composition comprising (A) polyvinyl alcohol, (B) a chitosan of which aqueous 1% solution has a viscosity not greater than 70 centipoise at 20° C. and (C) an aldehyde compound. 
     
     
       13. A water resistant composition as claimed in claim 12, wherein said aqueous 1% solution of said chitosan (B) has a viscosity of from 1 to 30 centipoise at 20° C. 
     
     
       14. A water resistant composition as claimed in claim 13, wherein said aqueous 1% solution of said chitosan (B) has a viscosity of from 1 to 10 centipoise at 20° C. 
     
     
       15. A water resistant composition as claimed in claim 12, wherein said aldehyde compound (C) is a water soluble aldehyde compound. 
     
     
       16. A water resistant composition as claimed in claim 15, wherein said aldehyde compound (C) is one or more compounds selected from the group consisting of water soluble monoaldehydes, polyaldehydes, condensation products of amines and formalin, methylolamides, urea formalin resins and melamine formalin resins. 
     
     
       17. A water resistant composition as claimed in claim 16, wherein said aldehyde compound (C) is glyoxal or hexamethylenetetramine. 
     
     
       18. A water resistant composition as claimed in claim 12, wherein the ratio by weight of said polyvinyl alcohol (A) to said chitosan (B); [(A)/(B)] is from 99/1 to 10/99, and the ratio by weight of said polyvinyl alcohol (A) and said chitosan (B) to said aldehyde compound (C); {[(A)+(B)]/(C)} is from 100/1 to 100/20. 
     
     
       19. A water resistant composition comprising (A) a modified polyvinyl alcohol having a silyl group in the molecule, (B) a chitosan of which an aqueous 1% solution has a viscosity not greater than 70 centipoise at 20° C. and (C) an aldehyde compound. 
     
     
       20. A water resistant composition as claimed in claim 19, wherein said modified polyvinyl alcohol (A) having silyl group in the molecule is a hydrolyzed product of a copolymer of a vinyl ester and an olefinically unsaturated monomer having silyl group in the molecule. 
     
     
       21. A water resistant composition as claimed in claim 19, wherein said modified polyvinyl alcohol (A) contains from 0.01 to 10% by mole of silyl group-containing monomer units. 
     
     
       22. A water resistant composition as claimed in claim 19, wherein said modified polyvinyl alcohol (A) contains from 0.1 to 5% by mole of silyl group-containing monomer units. 
     
     
       23. The water resistant composition of claim 19, wherein said aqueous 1% solution of said chitosan has a viscosity of from 1-30 centipoise at 20° C. 
     
     
       24. The water resistant composition of claim 23, wherein said aqueous 1% solution of said chitosan has a viscosity of from 1 to 10 centipoise at 20° C. 
     
     
       25. The water resistant composition of claim 19, wherein said aldehyde compound is a water soluble aldehyde compound. 
     
     
       26. The water resistant composition of claim 25, wherein said aldehyde compound is at least one compound selected from the group consisting of water soluble monoaldehydes, polyaldehydes, condensation products of amines and formalin, methylolamides, urea-formalin resins and melamine-formalin resins. 
     
     
       27. The water resistant composition of claim 26, wherein said aldehyde compound is selected from the group consisting of glyoxal and hexamethylenetetramine. 
     
     
       28. The water resistant composition of claim 19, wherein the ratio by weight, (A)/(B), of said modified polyvinyl alcohol having a silyl group in the molecule (A) to said chitosan (B) is from 99:1 to 10:99, and the ratio by weight, (A)+(B)/(C), of said modified polyvinyl alcohol having a silyl group in the molecule (A) and said chitosan (B) to said aldehyde compound (C) is from 100:1 to 100:20.